The present invention relates generally to filters and more particularly to fuel filters for filtering particulate impurities from liquid fuels such as diesel or gasoline.
Fuel filter assemblies are used in combustion engines for filtering particulate impurities from liquid fuels such as gasoline or diesel. A common form of fuel filter assembly includes a filter cartridge mounted in the filter chamber of a filter housing. The filter element removes particulates and water from the fuel as it travels radially inward through the filter element to the standpipe. The filter cartridge includes a tubular filter element which is situated concentric around a standpipe extending vertically from the base of the filter housing. A valve in the standpipe has open and closed positions to control fuel flow through the fuel filter assembly. The filter cartridge includes an axial projection that depresses and opens the valve when the filter cartridge is installed in the filter housing.
After a certain amount of time the filter media in the filter element tends to collect a large quantity of impurities. To remedy this problem, the filter element is periodically removed from the filter housing, disposed of, and then replaced with a new filter element, typically at scheduled maintenance intervals.
There have been two prior art approaches for facilitating to replacement of the filter element. The first approach has been to replace the filter element but reuse the existing lid as taught by Popoff et al. in U.S. Pat. No. 6,015,492. According to this approach, the filter element is releasably latched to the lid such that the filter element can be removed from the lid and then replaced with a new element. The other approach has been to replace the entire filter cartridge. One attempt demonstrating this second approach is taught by Popoff et al. in U.S. Pat. No. 4,836,923 with the exception that the filter housing in that attempt does not have an actuatable valve in the standpipe. According to this second approach, the filter element is permanently secured to the lid by potting the filter media of the filter element directly to the bottom side of the lid, such that the entire filter cartridge is disposable and replaceable.
There are several problems existing with both approaches. One problem with the first approach is that excessive fuel to skin contact occurs when the mechanic removes the filter element from the lid and replaces it with a new element. Excessive handling of the used filter element is needed for removal and disposal. Another problem with this approach is that a dirty and used outer gasket is left on the lid to be reused for sealing between the cartridge and the filter housing. Undesirable particulates can build up at this location that in turn can cause problems. Furthermore, if the gasket is lost or becomes faulty, fuel leakage can occur between the filter housing and the lid of the filter cartridge. Even when a new gasket is provided with the replacement filter element, there is no guarantee that the mechanic will take the time to throw away the old gasket.
A problem with the second approach in which the entire filter cartridge is disposable as taught by Popoff et al. in U.S. Pat. No. 4,836,923, is that the filter element is potted into the lid which can cause installation, sealing and alignment difficulties. In particular when the filter element is directly potted to the lid, it is difficult to properly position the filter element perfectly concentric with the lid during manufacture. This in turn makes it difficult for the sealing grommet to properly align and seal with the center standpipe due to these and other manufacturing tolerances. This is further complicated by the fact that the helical structure of the threaded connection between the cartridge and housing can cause a slight tilt in the filter cartridge during installation. A further problem with this approach as alluded to above is that there is no valve structure in the standpipe of the housing. Other problems with this second approach are also recognized in the ""492 patent.
It is also known to provide an outer strainer basket as part of the filter cartridge that concentrically surrounds the ring of filter media in the filter element. According to this type of cartridge, the strainer basket a plastic member that is integrally molded with the top plastic end cap of the filter element. However, the addition of a strainer basket adds one additional structure which also presents manufacturing tolerance difficulties. In particular, the top plastic end cap of the filter element becomes an extremely complex and costly part to form. Again it is also difficult to properly pot the ring of filter media of the filter element into this top end cap using potting compound. It is easy for the top end cap and therefore the strainer basket to be misaligned or otherwise not concentric with the rest of the filter element including the grommet carried by the bottom end cap of the filter element. Because the strainer basket carries a radial seal gasket which is intended to form a radial seal, this design presents the problem of concentric misalignments between the grommet and the radial seal gasket carried by the basket, which in turn can cause installation difficulties and sealing problems when the filter cartridge is installed into the filter housing.
A further desirable aspect of any fuel filter cartridge is to provide a mechanism that prevents a mechanic or vehicle operator from removing the filter element and replacing the lid without the filter element such that unfiltered fuel can be run through the system. Running unfiltered fuel through an engine could eventually lead to engine damage or failure. All of the difficulties are not easy to resolve, particularly where there is also a desire to provide for an inexpensive filter cartridge.
The present invention is directed towards a novel disposable filter cartridge, in which the entire filter cartridge is disposable. The filter cartridge includes a tubular filter element substantially permanently retained to a lid such that the filter element cannot be removed from the lid without extreme force that would likely break or damage the filter cartridge. The filter element includes a ring of filter media having ends potted in disc shaped end caps. The lid includes a central hub that is inserted through the opening in one of the end caps and ultrasonically deformed or flared radially outward to provide a lip that engages the end cap for axial retention. The filter element is free floating and can be moved a small degree axially and also freely rotated relative to the lid. This provides significant advantages during installation of the filter cartridge into the filter housing where the grommet tightly engages the standpipe and can provide significant frictional resistance. By allowing a controlled amount of play both axially and rotationally, the present invention greatly eases the difficulty of installing the cartridge and ensuring proper installation including proper compression and location of seals and grommets to ensure proper sealing. The lid also integrally provides an axial projection inside of the central hub for actuating the valve in the filter housing standpipe.
Other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.